The field of the invention pertains to biomechanical strength testing of individual persons and, in particular, to the careful isometric strength testing of individuals disabled as a result of injuries. Strength testing relates to disability evaluations, pre-employment examination, job redesign and work conditioning.
In recent years, the importance of careful biomechanical modeling and the repeatability of results from strength testing to assure validity of the results has taken on great importance to assure that the physical labor required in a job is properly matched with the individual worker. More importantly, avoidance of injury and the proper evaluation of disabling injuries has become important not only because of the cost to the disabled but also the cost to society that also results.
Extensive research and careful analysis of the human body structure under physical stress is disclosed and summarized in a recent book by Don B. Chaffin, Ph.D. and Gunnar Andersson, M.D. entitled, "Occupational Biomechanics", 1984 John Wylie & Sons, Inc. The book presents extensive biomechanical guidelines and considerations for the physical work and workplace of an individual. On the bases of these guidelines and considerations, limits are suggested for various physical activities in various workplace situations.
A publication by the U.S. Department of Commerce, National Technical Information Service, sponsored by the U.S. Department of Health and Human Services, is entitled, "Work Practices Guide for Manual Lifting" and was published in March of 1981 with reference number TB 82-178948. This technical report summarizes research on the hazards of manual materials handling in industry and recommends means to reduce the human and economic burden imposed by improper materials handling. Such recommendations include the safe load, weight, size, location and frequency of handling by a worker. Worker training and selection criteria are listed and engineering guidelines are provided for the design of the workplace.
At the University of Michigan in Ann Arbor, Mich., an isometric strength testing machine was developed with an electric sensor or load cell employed to sense the load applied to the machine by the subject individual. The purpose of the machine is for job analysis and employment screening and the electric sensor is directly connected to interface means to directly record the load applied to the machine by the subject. The machine and considerable supporting mainframe computer software was developed under a National Aeronautics and Space Administration supported contract. The principal publication arising from the research is Garg, A. and Chaffin, D. B., The Human Strength Simulations, Biomechanical Division NASA/MSC Contract #NAS9-10973, April 1972.
The machine comprises a vertical assembly post and a horizontal platform. At various heights on the vertical assembly post, a horizontal arm may be positioned. The horizontal arm contains the necessary sensor and a single or double hand grip for the subject to apply a load to the machine. Depending on the height of the hand grip, the subject may be in various postures, such as partially bent over to lift a load from the platform, pushing against the hand grip, or raising a load over the subject's head. As a result of the development of the machine and the mainframe software, considerable research was accomplished in job analysis and employment screening.